Dual-Bridge LLC Resonant Converter With Fixed-Frequency PWM Control for Wide Input Applications

This paper proposes a dual-bridge (DB) LLC resonant converter for wide input applications. The topology is an integration of a half-bridge (HB) LLC circuit and a full-bridge (FB) LLC circuit. The fixed-frequency pulsewidth-modulated (PWM) control is employed and a range of twice the minimum input voltage can be covered. Compared with the traditional pulse frequency modulation (PFM) controlled HB/FB LLC resonant converter, the voltage gain range is independent of the quality factor, and the magnetizing inductor has little influence on the voltage gain, which can simplify the parameter selection process and benefit the design of magnetic components as well. Over the full load range, zero-voltage switching (ZVS) and zero-current switching (ZCS) can be achieved for primary switches and secondary rectifier diodes, respectively. Detailed analysis on the modulation schedule and operating principle of the proposed converter is presented along with the converter performance. Finally, all theoretical analysis and characteristics are verified by experimental results from a 120-V to 240-V input 24 V/20 A output converter prototype.